Servais has been with Club Brugge since 2017. The 17-year-old left winger came over from Sporting Charleroi's youth academy. In July 2020, Mathis signed a professional contract with Blauw-Zwart. That same year, he made his debut for Club NXT in the Challenger Pro League.
In the preparation for this season, he picked up minutes in practice matches with the A-core and managed to score a nice free kick himself.